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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

MTT,ES AND GRINNELL GLACIERS
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to heights of 8000 to 10,000 feet near the head of the Miles Glacier. Within the mountain valley the glacier has a width of two to two and a half miles and it receives at least three tributaries in its lower course. There are one or two rather weak medial moraines, but there are broad lateral moraines; that on the north having a width of an eighth of a mile, while the southern lateral is half a mile to a mile in width. Throughout its visible course, in this mountain valley, this ice stream is severely crevassed.
Where it emerges into the Copper River valley, the Miles Glacier spreads out in a great bulb, the width increasing from 2$ miles in the mouth of the valley to 6| miles, measured from the northern to the southern edge. This bulb has two quite different portions, a precipitous ice wall on the south, and a moraine-covered piedmont area in
FIG. 60.   MAP TO ILLUSTRATE SIZE or CHILDS AND MTT,™ GLA.CHIHS.
the northern portion. The southern half protrudes only slightly from the mountain valley, ending in a vertical, white, ice cliff (PL CLVIII, B) which discharges icebergs into the lake-like expanse of Copper Biver caused by the Childs Glacier constriction just below. This cliff is about three and a half miles long and at least 200 feet high. On the southern border of this clear ice terminus is a detached strip of ice completely mantled by morainic debris, making it impossible to judge exactly where the ice ends. This is opposite the terminus of the broad strip of lateral moraine, barren of vegetation, which extends up the southern border of the glacier.
The northern half of the Miles Glacier terminus, into which the ice cliff grades, projects westward a distance of three and a half miles, forcing the Copper River clear across the valley and into a marginal channel on the western side, where the constriction causes Abercrombie Rapids. This part of Miles Glacier looks so little like a glacier